如何在Symfony 2.8中将数据库数据导出到csv

Question

我开发了以下成员函数来下载带有表数据的csv文件。但是我也收到带有键的单行数据。如何仅逐行获取值（每一行中的每个记录）。请帮忙。

   /**
     * @Route("admin/newsletter/export", name="NewsLetterExport")
     */
    public function NewsLetterExportAction(Request $request)
    {    
        $subscriberObj = $this->getDoctrine()
                         ->getRepository(NewsLetterEntity::class)
                         ->findAll();

        $data = $this->encode($subscriberObj);

        $response = new Response($data );
        $response->setStatusCode(200);
        $response->headers->set('Content-Type', 'text/csv; charset=utf-8');
        $response->headers->set('Content-Disposition', 'attachment; filename="export.csv"');
        return $response;

    }